Regressing and progressing Moloney sarcomas are being disaggregated for the purpose of recovering contained inflammatory cells (IC). The various IC types have been quantified, and found to consist primarily of T lymphocytes and macrophages. Methods have been developed to enrich these cell types and to test their cytotoxic activities separately in vitro. Both T lymphocytes and macrophages from regressing tumors were cytotoxic, the former in an antigenically specific manner, while the latter killed without regard to antigenic specificity. Correlative ultrastructural studies of IC in vitro and within the tumor are underway. Emphasis currently is on determining how T cells and macrophages reach tumors (homing) and what effects purified populations of these IC have on the growth of sarcomas in immunologically compromised hosts (adoptive transfer/protection studies). Also under study are the interrelationships between T cells and macrophages in tumors, as well as alterations in function which may characterize IC recovered from progressing neoplasms. BIBLIOGRAPHIC REFERENCE: Russell, S.W., G.Y. Gillespie, C.B. Hansen and C.G. Cochrane. Inflammatory cells in solid murine neoplasms. II. Cell types found throughout the course of Moloney sarcoma regression or progression. Int. J. Cancer, September, 1976.